Astronomers have made a significant breakthrough in exoplanet research by creating the first three-dimensional map of WASP-18b, a planet located approximately 400 light-years from Earth. Utilizing the advanced capabilities of the James Webb Space Telescope, researchers employed a novel technique known as 3D eclipse mapping or spectroscopic eclipse mapping. This method allows scientists to monitor subtle changes in light wavelengths as WASP-18b transits behind its star, enabling them to reconstruct temperature variations across the planet’s atmosphere.
The mapping process revealed distinct temperature zones throughout WASP-18b’s atmosphere. According to Ryan Challener, a postdoctoral associate at Cornell University and the lead author of the study, “If you build a map at a wavelength that water absorbs, you’ll see the water deck in the atmosphere, whereas a wavelength that water does not absorb will probe deeper.” By combining these observations, the team successfully created a comprehensive 3D temperature map.
Located about 400 light-years away, WASP-18b is an intriguing celestial body with roughly ten times the mass of Jupiter. It orbits its host star in just 23 hours, which subjects it to extreme temperatures that can reach nearly 5,000 degrees Fahrenheit (2,760 degrees Celsius). These intense conditions made WASP-18b an ideal candidate for testing the new mapping technique.
The 3D map unveiled a striking hot spot at the center of the planet’s dayside, surrounded by a cooler ring. This unique atmospheric structure is attributed to the planet’s tidally locked orbit, meaning one side perpetually faces its star. Notably, the hot spot exhibited lower levels of water vapor than the overall atmospheric average. Challener noted, “We think that’s evidence that the planet is so hot in this region that it’s starting to break down the water. That had been predicted by theory, but it’s really exciting to actually see this with real observations.”
Advancing Exoplanet Research
The successful use of 3D eclipse mapping represents a significant advancement in the field of exoplanet observations. This technique allows astronomers to study exoplanets that cannot be directly observed due to the brightness of their host stars. Challener emphasized the potential of this method, stating, “As 3D eclipse mapping is applied to other exoplanets observed by Webb, we can start to understand exoplanets in 3D as a population, which is very exciting.”
The research team published their findings in the journal Nature Astronomy on October 28, 2025. This groundbreaking study not only sheds light on the atmospheric conditions of WASP-18b but also paves the way for enhanced understanding of exoplanets in general, marking a new chapter in the exploration of worlds beyond our solar system.
